This invention relates to a class of mortar training devices which are fired to approximately one-tenth the distance of service ammunition. The devices are intended to provide realistic mortar firing training, at low cost, using a standard mortar, standard sighting and fire control equipment, and a special firing table in the same manner as standard service mortar ammunition. In particular, the invention relates to a method of realistically simulating a standard propelling charge system including appearance, handling, operating procedures, and functions in a mortar training device.
Propelling charges for service use are typically horseshoe-shaped and stacked in a group of four charges about the boom of a fin-stabiized mortar projectile. The charges are assembled to the boom through the open end of the horse-shoe and snapped in place. Each charge may be removed indivually. Removal of one or more charges prior to drop-firing the projectile reduces the velocity of the projectile and thereby foreshortens flight time and distance of impact. Each velocity level is identified as a charge zone number, according to the number of charges employed, including Charge 0 where all charges are absent and only the ignition cartridge propels the projectile out of the weapon.
An effective training system permits or requires the trainee to perform a complete sequence of procedures in the same way as with standard service ammunition, with as much similarity in appearance, handling, feel and functionality of the materiel as is feasible, and with safety and low cost.
A major shortcoming of existing training devices is their inability to achieve the desired realism in handling and adjustment of propelling charges for zoning. Examples of this deficiency may be found with training devices in current use for the 81 mm mortar system, viz., the M880 Training Cartridge, and the M1 Sabot with 22 mm Sub-caliber Practice Cartridges M744, M745, M746 and M747.
The M880 Training Cartridge consists of a kit of expendable component assemblies and a full-size flight projectile of limited reusability. The kit contains a fuze w/ spotting charge, an ignition cartridge, and small plastic plugs. The components of the kit are pre-assembled in the field to the projectile. The small plugs are inserted into the inlet end of gas exhaust ports, the latter located in the main body of the flight projectile.
The trainee selects a desired charge zone by removing an appropriate number of plugs from the projectile prior to drop firing. The unplugged gas ports exhaust a portion of the propelling gases through the projectile body to debilitate energy delivered to the projectile.
The act of removing the plugs and checking the number of plugs remaining in-place prior to drop firing purports to correspond with service procedures for removal and checking of propelling charges. However, the plug arrangement fails in simulating size, configuration, locale, and method of removal relative to that of standard service propelling charges. Accordingly, the M880 Training Cartridge is deemed to lack the desired realism in this aspect of training.
The alternative M1 Sabot system with its sub-caliber cartridges is a training device which employs a sub-caliber flight projectile housed within a sabot projectile. The system fires the subcaliber projectile to a desired distance, while the sabot projectile is ejected a few yards from the mortar weapon. The subcaliber projectile contains a fuze and spotting charge to permit sighting of impact.
The M1 system has no means for ajusting the charge to achieve the desired range distance zoning. Instead, the trainee selects a specific sabot projectile which is pre-fitted with a sub-caliber cartridge having the appropriate charge level. The trainee is able to discriminate between the charge level of each projectile by inspection of identifying notches at the exposed base of each cartridge.
While both existing systems provide a means for selecting a charge zone, neither system provides the desired realism in simulating service conditions with respect to appearance and handling of propelling charges, viz., size, configuration and location of the charges, method of attachment to the boom of the projectile, technique for removal, and means for visual or nonvisual inspection.